Why was my credit card payment or refund declined?

If the website does not tell you the problem, there is regrettably little we can do to help. For security reasons, banks will not answer questions from anyone other than the account holder. If you cannot get the payment to go through, we recommend either you contact your issuing bank, or use a different card. 

If you are using an institutional or government credit card you may need to contact the responsible department to pre-authorize your charge. In previous years some registrants have run into problems with cards that are restricted to a very limited set of merchants or require advance notice on transactions over a certain amount.